JPH0533265B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention has properties such as lubricity, water repellency, light transparency, weather resistance, and antistatic property, and therefore these properties are required. The present invention relates to a molded article having a fluorine-containing thin surface layer used for various purposes.

(Prior art and its problems) Many attempts have been made in the past to provide a surface layer having characteristics not possessed by the base material on a base material made of a polymeric substance. A solution of a polymer containing a fluorine-based additive is wet-coated in the atmosphere onto a base material made of the same polymer, and then dried by heating to form a surface layer containing a fluorine-based additive on the base material. However, this method has the following drawbacks.

(b) When forming the surface layer, there is a wet process in which a polymer solution containing a fluorine-based additive is applied to the base material, so it is necessary to heat and dry the applied polymer solution, which reduces the melting point and transition point. Low thermoplastic polymer sheets and plastic molded products cannot be used as base materials because their dimensional stability is impaired.

(b) Recently, molded products with extremely thin and uniform surface layers have been industrially obtained using vacuum evaporation methods, sputtering methods, ion plating methods, etc., regardless of the shape, such as flat, spherical, uneven surfaces, etc. However, with the above-mentioned wet coating method of a fluorine additive-containing polymer solution onto a substrate, it is difficult to obtain a thin and uniform surface layer.

(c) Since a solvent is used, there is a risk of explosion or poisoning.

(d) Adhesion between the fluorine-containing additive-containing surface layer and the base material is insufficient, and the fluorine-containing surface layer is likely to peel off from the base material during use.

(e) The surface layer containing the fluorine-based additive dissolves and disappears during use, reducing its functionality.

A low-temperature plasma polymerization method is known as a method that solves the above-mentioned drawbacks of the conventional technology in which a surface layer containing a fluorine-based additive is formed on a substrate by a wet process. Below, a discharge plasma of a carrier gas such as N ₂ , Ar, He, etc. is mixed with a monomer organic gas, and by bringing these mixed gases into contact with the surface of the substrate to be treated, a plasma polymerized film is formed on the surface of the substrate. It is something. The formation of this polymeric film was described by JLVossen and W.
“Thin Film Processes” Academic, edited by Kern
Press, New York (1978) p. 365 CAP diagram (Competitive Ablation and Polymerization)
It is thought that this phenomenon is caused by a competing reaction between polymerization and ablation, as shown in Scheme 1.

However, the plasma polymerization method described above is an extremely effective method for forming a polymer film of compounds containing nitrogen, silicon, and unsaturated bonds on the surface of a substrate, but it is not suitable for forming a polymer film of compounds containing nitrogen, silicon, and unsaturated bonds on the surface of a substrate. The drawback was that it was difficult to form a polymer film on a substrate.

Therefore, in order to eliminate the drawbacks of the plasma polymerization method described above, for example, H ₂ gas or silicon element is added to the reaction system (2). In particular, for base materials that do not contain hydrogen or do not appear, _H2 gas is added to the reaction system.() As a monomer raw material, a reaction system fluorine compound having a carbon-carbon double bond such as tetrafluoroethylene using ()
Polyethylene, polypropylene, etc. are used as base materials.
A fluorine-containing surface layer has been formed on a substrate by a plasma discharge method using a polymer in which H ₂ appears (E. Kay, IUPAC
Symposium on plasma Chemistry，Limoges，
France (1977) and T. Masuoka, H. Yasuda,
J. Polym, Sci., 20, 2633-2642 (1982)),
While this method achieves its purpose in terms of forming a fluorine-containing surface layer on the substrate, it also
There were drawbacks such as the risk of explosion due to _H2 gas and the risk of explosion and poisoning due to the fluorine compound containing carbon-carbon double bonds.

On the other hand, by bringing an organic polymer compound such as polyethylene or polypropylene into contact with fluorine-containing plasma generated from fluorine hydrocarbons or fluorocarbons such as CF ₄ or CHF ₃ , the surface area of the organic polymer compound is exposed to fluorine. A method has been proposed in which a substance is introduced and modified (Japanese Patent Application Laid-open No. 55-99932). In addition to the above problem (), this method has the disadvantage that roughness is formed on the surface of the material to be modified due to etching.

(Objective of the Invention) The object of the present invention is to improve the above-mentioned drawbacks of the prior art and to provide various properties such as lubricity, water repellency, light transmittance, weather resistance, and antistatic property. An object of the present invention is to extremely safely provide a molded article having a thin fluorine-containing surface layer, which can be used in various applications requiring fluorine.

(Means for Solving the Object) As a result of various studies, the present inventors recognized that although it has advantages such as nonflammability, it is non-reactive, and it is difficult to form a thin layer on a base material by conventional plasma treatment. Surprisingly, sulfur fluoride compounds such as SF ₆ , which had been thought to be effective, have surprisingly been produced by plasma discharge into a strong fluorine-containing thin film that has lubricity, water repellency, light transparency, weather resistance, antistatic properties, etc. It was discovered that the layer can be formed without changing the properties of the base material as a whole, and the present invention was completed based on this knowledge.

That is, the gist of the present invention is a molded article having a fluorine-containing thin surface layer formed by forming a fluorine-containing thin layer on a base material by subjecting a sulfur fluoride compound to plasma treatment.

As the fluorine compound used as a raw material in the production of the molded article of the present invention, any sulfur fluoride compound that is gasified at room temperature or gasified at the temperature during discharge treatment can be used. Examples include SF ₆ , which has properties such as corrosion resistance and non-corrosion properties. This can be used alone or in combination, and for the purpose of adjusting the discharge voltage, an inert gas such as N ₂ ,
It can also be used after being diluted with a gas such as Ar or He.

Further, examples of the base material used in the production of the molded article of the present invention include natural polymers, synthetic polymers, ceramics, etc., and these may be used alone or in a mixture.

Examples of the above-mentioned natural polymers include cotton, hemp, silk, wood, etc., and examples of synthetic polymers include:
Nylon, polyester, polycarbonate, polyacetal, polysulfone, polyether sulfone, polyester ether ketone, polyacrylate, polyimide, polyaramid, polyvinyl alcohol, polyurethane, polymethacrylate, polycellulose, polyepoxide, polyvinyl chloride, etc., and ceramics include , glasses such as silicate glass, quartz glass, borate glass and phosphate glass, cements such as alumina cement, Bortland cement and magnesia cement, porcelains such as zircon porcelain, alumina porcelain and titanium porcelain. In addition, inorganic substances such as copper, aluminum, iron, nickel and indium, oxides,
Examples include amorphous amorphous or alloys. this is,
They may be used alone or in combination, and may also be fibrous,
It may be of any shape, such as a plate, sheet, or block.

A plasma discharge apparatus preferably used in plasma processing using a sulfur fluoride compound is basically composed of a raw material vapor supply system, a carrier gas supply system, a plasma generation system, a plasma reaction system, and an exhaust system. For example, in a plasma discharge device using microwave discharge, a raw material supply system includes a raw material vapor tank and a flow meter to supply raw material vapor to a plasma reaction vessel. The carrier gas supply system includes a gas storage tank and a flow meter and supplies the gas to be turned into plasma to the plasma generation system. The plasma generation system includes a directional coupler, a three-stub tuner, a magnetron oscillator, and a plasma generation region or tube, and one end of the plasma generation region is connected to a plasma reaction vessel. The plasma reaction vessel forms the main body of the plasma reaction system and is equipped with a capacitance meter and a processing object support device. Furthermore, an exhaust system equipped with an oil rotary pump is provided to exhaust the inside of the reaction vessel.

To perform plasma treatment using the sulfur fluoride compound used in the present invention, plasma generation methods include direct current glow discharge and low frequency discharge using an internal electrode method, high frequency discharge using an internal electrode method, external electrode method, and coil method, and conduction. There are microwave discharge using a wave tube type method and electron cyclotron resonance discharge (ECR discharge), but other methods can also be used as long as they generate plasma and cause a reaction that forms a thin layer. Can be used. In addition, in the case of the internal electrode method, the electrodes used in the present invention include Al, Ti, Sn, Ge, Si,
Examples include metals containing Au, P, As, etc. In the case of a discharge method other than the internal electrode method, other than the above may be used.
Examples include metals containing Mo, B, W, U, etc.

As the plasma generating apparatus of the present invention, either the plasma discharge apparatus using high frequency discharge shown in FIG. 2 or the plasma discharge apparatus using microwave discharge shown in FIG. 3 can be used.

The thickness of the thin surface layer formed can be arbitrarily varied depending on the intended use of the molded product, etc.
For example, a layer thickness of 0.001 to 10 μm provides sufficient antistatic performance. If productivity is required for films, sheets, etc., continuous production is possible with a thickness of 0.001 to 0.1μ.

(Example) The present invention will be further explained with reference to Examples below.
The present invention is not limited to these examples.

Reference example 1 (1) Commercially available polyethylene terephthalate film (hereinafter abbreviated as PET film) was used as the base material.
A PET film was subjected to plasma discharge treatment using CF ₄ as a raw material gas and a plasma discharge device using high frequency discharge shown in FIG. 2 as a plasma discharge device.

The plasma discharge apparatus shown in FIG. 2 includes a plasma generation system (high frequency power source) 1, a plasma reaction system 2, a raw material, a carrier gas supply path 3, and an exhaust path 4.
In the plasma reaction system 2, a pair of aluminum electrodes 5, 5' are arranged with an interval of 1.5 cm, and a circular PET with a diameter of 3.2 cm, which is the object to be processed, is placed on the lower electrode 5'. film 7
has been set.

CF ₄ as a raw material gas is introduced into the plasma reaction system 2 via the raw material and carrier gas supply line 3 at a flow rate of 5 to 50 cm ³ /min under a pressure of 1 to 4 Torr, and at a level of 50 W to 13.56 MHz. A high frequency power of 0.25 is applied to the electrodes 5 and 5' to cause a discharge.
A thin surface layer was formed on the PET film by plasma discharge treatment for ~30 minutes. Furthermore, PET during discharge
The temperature of the film was not particularly controlled, but was kept below the glass transition temperature (69°C).

(2) As a result of measuring the ESCA spectrum (X-ray photoelectron spectrum) of the surface thin layer of the obtained plasma discharge treated PET film, the formation of -CF ₂ - bonds originating from the fluorination of the benzene ring was observed, = Since no CF-bond formation was observed, it is inferred that this surface thin layer has the following structure.

The thickness of this thin surface layer was found to be approximately 0.002μ by ESCA analysis.

(3) Next, the changes in the water drop contact angle θ as a function of the plasma discharge treatment time t are shown in FIGS. 1a, b, and c. In this figure, one dot means the average value of 3 to 4 measurements. Untreated
The contact angle of the PET film was 70° (t=0 min), which was consistent with literature values. Figure 1 a, b,
c, it is recognized that the contact angle depends on the treatment time even if the raw material gas flow rate and pressure are varied; once the discharge treatment begins, the contact angle increases rapidly, reaching 100 to 110° in 10 to 20 minutes. reach and then
It became constant.

Since the contact angle of polytetrafluoroethylene (PTFE) is 108°, the PET film surface treated with _CF4 plasma discharge for 10-20 minutes in this example was found to have hydrophobicity equivalent to that of PTFE. It was also confirmed that the measurement results approximately 24 hours after the treatment and the measurement results of the same sample approximately 2 months later held consistent values within the error range.

(4) Furthermore, using a scanning electron microscope (SEM),
As a result of observing the surface roughness of the thin surface layer of the plasma discharge treated PET film, it was found that this thin surface layer had a uniform roughness resulting from etching compared to the untreated PET film.

Reference Example 2 (1) A PET film was subjected to plasma discharge treatment using a PET film as a base material, CF ₄ as a raw material gas, and a plasma discharge device using microwave discharge shown in FIG. 3 as a plasma discharge device.

The plasma discharge apparatus shown in FIG. 3 includes a plasma generation system (magnetron) 1, a plasma reaction system 2, a raw material, a carrier gas supply path 3, and an exhaust path 4.
Alumina tubes 6, 6' were arranged inside the reaction system 2, and a rectangular (4.5 x 2.5 cm) PET film 7, which was the object to be treated, was set on the inner wall.

CF ₄ , which is a raw material gas, is introduced into the plasma reaction system 2 under the same conditions as in Reference Example 1 via the raw material and carrier gas supply path 3, and the power is 2450M at a level of 160W.
A discharge is caused by microwave power at Hz, 0.25 to 30
A thin surface layer was formed on the PET film by plasma discharge treatment for minutes. Although the temperature of the PET film during discharge was not particularly controlled, it was kept below the glass transition point (69°C).

(2) As a result of measuring the ESCA spectrum of the surface thin layer of the obtained plasma discharge PET film, it was confirmed that it had the same structure as the surface thin layer of the plasma discharge PET film obtained in Reference Example 1.

(3) Next, FIG. 1d shows the change in the water droplet contact angle θ as a function of the plasma discharge treatment time t. In this figure, one point (dot) means the average value of 3 to 4 measurements. From FIG. 1d, the contact angle rapidly increased when the discharge treatment started, reached about 105° in 20 minutes, and then became constant. Therefore, in this example, the surface of the PET film treated with CF ₄ plasma discharge for 20 minutes was found to have hydrophobicity equivalent to that of PTFE. Furthermore, it was confirmed that the measurement results about 24 hours after the treatment and the measurement results of the samples about 2 months later also held consistent values within the error range.

(4) Furthermore, using a scanning electron microscope (SEM),
As a result of observing the surface roughness of the surface thin film layer of the plasma discharge treated PET film, this surface thin layer had the same smoothness as the untreated PET film, and in this respect, the plasma discharge treated PET film of Reference Example 1 had a uniform roughness. It was found that this was different from the surface thin layer of discharge treated PET film.

Example (1) PET film as base material, SF ₆ as raw material
Plasma discharge treatment was carried out using the same plasma discharge apparatus as in Reference Example 1.

The raw material SF ₆ was introduced into the plasma reaction system 2 together with an inert gas He at a flow rate of 10 scc/min under a pressure of 1 to 2 Torr (Torr), and at a level of 30 W.
A high frequency power of 13.56 MHz was applied to the electrode to generate a discharge, and a thin layer was formed on the PET film by plasma discharge treatment for 1 to 30 minutes.

(2) Plasma discharge treatment time t for water droplet contact angle θ
The variation as a function of is shown in Figure 1e. In this figure, one point (dot) means the average value of 3 to 4 measurements. From Figure 1e, the contact angle increases rapidly when the discharge treatment begins, and approximately
It reached 108° and then became constant. Therefore, in this example, the sample was treated with SF ₆ plasma discharge for 20 minutes.
It was found that the PET film surface has hydrophobicity equivalent to that of PTFE.

(Effects of the Invention) The molded product having a thin fluorine-containing surface layer of the present invention uses a sulfur fluoride compound that has low toxicity, non-flammability, and non-corrosion properties during its manufacture, so it is more effective than conventional plasma discharge treatment. It has the advantage of being safe with little risk of explosion.

Furthermore, the molded article having a fluorine-containing thin surface layer of the present invention has properties such as lubricity, water repellency, light transmittance, weather resistance, antistatic property, and smoothness, and is preferably used in the following applications.

(b) Magnetic tapes, magnetic disks, optical recording disks, magnetic tape leader tapes and trailer tapes that require lubricity, sliding parts of precision equipment such as cameras and watches, sliding parts of ceramic artificial bone joints, etc. (b) Waterproof map information film that requires water repellency, moisture-proof film for pharmaceuticals and precision equipment, nets for the fishing industry, vehicle window materials including sunroofs, and windows including those for high-rise buildings. materials, roof tiles, rain gear such as umbrellas, packaging packages, etc. (c) Agricultural films for growing plants that require light transparency, films for solar collectors, infrared absorption cells, etc. (d) Weather resistance is required Outdoor roofing materials that are lightweight and have the effect of reducing daytime certification costs, etc. (e) Dust-proof wall materials that require antistatic properties, photolithography films, dust-proof clothing, records, etc., (d) Other artificial materials. Medical materials such as defects, artificial organs, blood bags, porous materials that highly separate oxygen, hydrogen, etc.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between water drop contact angle and treatment time for the plasma-treated film of the present invention and the plasma-treated film of Comparative Example 1. Figure 2 is a graph showing the plasma discharge by high-frequency discharge used in the production of the molded article of the present invention. Schematic diagram of the apparatus. FIG. 3 is a schematic diagram of a plasma discharge apparatus using microwave discharge used in manufacturing the molded article of the present invention. 1... Plasma generation system, 2... Plasma reaction system, 3... Raw material, carrier gas supply path, 4... Exhaust path, 5, 5'... Electrode, 6, 6'... Tube, 7...
Object to be processed.

Claims (1)

[Scope of Claims] 1. A molded article having a fluorine-containing thin surface layer formed by forming a fluorine-containing thin layer on a base material by subjecting a sulfur fluoride compound to plasma treatment. 2. The molded article according to claim 1, wherein the sulfur fluoride compound is SF ₆ . 3. The molded article according to claim 1, wherein the plasma treatment is performed by high frequency discharge or microwave discharge. 4. The molded article according to claim 1, wherein the base material is one type of material selected from the group consisting of natural polymers, synthetic polymers, and ceramics. 5 The base material is at least two selected from the group consisting of natural polymers, synthetic polymers, and ceramics.
The molded article according to claim 1, which is a mixture of seed materials. 6. The molded article according to claim 4 or 5, wherein the synthetic polymer is polyethylene terephthalate.